In all wheel drive (AWD) and four wheel drive systems in motorized vehicles, the front and rear axles can be coupled via an electromagnetic clutch which enable all of the vehicle's wheels to rotate in relation to one another. These vehicles can also be equipped with driver assistance systems, such as, stability control, traction control, and anti-lock brake systems (ABS). When a stability event occurs, and the vehicle's stability control, traction control, and/or ABS system is in use, the wheels can be decoupled from each other so that they can rotate and react independent of each other. The effectiveness of the driver assistance systems depends on the time it takes to decouple the vehicle's wheels; front-to-rear and side-to-side. If the vehicle's wheels are not decoupled quickly then activation of the vehicle's driver assistance systems will be delayed.
The response time of the stability control system is dependent on the time it takes to decay the current in a circuit which creates the electromagnetic field. In addition, the torque in an electromagnetic clutch system is dependent on the amount of current flowing through a coil which is used to create the electromagnetic field. The rate at which the electromagnetic field is created is directly proportional to the rate at which the current builds in the system. Likewise, the rate at which the magnetic field collapses in a system is proportional to the rate at which the current decays in the coil. Thus, the rate at which the current decays in a coil is proportional to the resistance in the circuit. The lower the resistance in the circuit the faster the circuit decays, causing the torque of the electromagnetic clutch to decay at a rate that is proportional to the current decay of the clutch coil.
Therefore, it is desirable to develop a circuit design where the current in a coil dissipates quickly in order to quickly decay an electromagnetic field, and the current passing through the coil creates an electromagnetic field quickly.